Contrivance of covalent organic framework membranes enabled by mixed dimensional self-assembly strategy for molecular separation

Abstract

Covalent organic frameworks (COFs) with tunable porous network structures afford unheard-of opportunities for high-efficient solvents-resistant molecular separation. Presently, the practicability of COFs membranes is critically constricted by its inflexible essence, weak interlaminar interaction and wider pore size, enabling the arduous preparation of defect-free membranes. In this work, a series of composite nanofiltration membranes were formed via a mixed dimensional assembly of COF-TAPT-BTA nanosheets and silk nanofibrils (SNF). The SNF with large aspect ratio and well-supplied functional groups effectively reduced the pore entrance of COF-TAPT-BTA (shielding effects) and intensified membrane's integrity. The interweaving and interlocked nanopore render the resultant COF@SNF-X membranes with precise molecular sieving abilities besides the augmented stability arose from the multiple interaction. Accordingly, the optimized COF@SNF-X membrane manifested an ultrahigh methanol permeance of 1365.5 L m⁻² h⁻¹ bar⁻¹ with a high rejection of 96.0 % for DR 23.